There are two main types of methods for manufacturing dressed thermoset-based headliners: two-step manufacturing methods and one-step manufacturing methods.
In the case of so called two-step manufacturing methods, the first step is for press thermo-forming the headliner substrate and the second step is for dressing up the headliner with a dressing layer.
In the case of one-step manufacturing methods, shaping and dressing of the headliner occurs at the same time by simultaneously press thermo-forming of all headliner layers, including the dressing layer.
The complexity and the costs of two step methods are higher than for one-step methods, but on the other side the complexity of the finished perimeter of dressed headliners strongly depend on the manufacturing method for the whole dressed headliner.
The finishing of the perimeter of a two-step manufacturing process of a thermoset headliner is relatively easy considering that the sharpness of the perimeter is achieved in the first substrate shaping step, and the final wrapping of the perimeter is easily achieved at the end of the second step of dressing of the headliner. U.S. Pat. No. 4,986,865 and U.S. Pat. No. 7,147,276, disclose substantially known methods according to that described above.
On the other hand, in the case of one-step manufacturing headliner method, there are two options.
The less complex one can be carried out by simply cutting out the headliner once it has been shaped and dressed without any other further operation, that is, without wrapping its perimeter. This simple method is compatible with any headliner manufacturing technology but it renders a low finishing quality of the headliner perimeter.
Second option allows a high quality finishing of the perimeter but it is much more complex considering that it should be carried out once the headliner is shaped and fully dressed.
That means that for a high quality finishing of the perimeter of a one-step thermoset headliner requires adhesive addition making difficult to control such finishing method.
Additionally the use of additional adhesives can damage the headliner, specially the dressing layer, e.g. due to possible adhesive leaks when adhesive addition stain the dressed headliner or dirty the headliner or the tools. U.S. Pat. No. 6,161,895 discloses a substantially known method according to that described above.
It is also known an intermediate case for finishing the perimeter of the one-step manufactured headliners. In order to finish the perimeter of the headliner, it is necessary to carry out a cutting step of a strip of the headliner, in particular, a strip of substrate of the headliner, leaving an excess of the dressing layer to wrap the perimeter of the headliner. In order to remove the strip of substrate, water steam can be applied on it. European patents EP1627720, EP1518663 disclose substantially known methods according to that described above.
Therefore, in order to overcome the drawbacks of the state of the art, the main objective of the invention is to achieve a dressed headliner for vehicles with a high quality finished perimeter without using additional materials to form this finished perimeter.